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USGS Professional Paper Notes for the Acrobat Version of PP901 Professional Paper 901 contains a history of geologic maps of the conterminous USA and a description of the compilation of the 1974 map. Presently, PP901 remains out of print and no longer available. For this CD-ROM publication, digital versions of PP901 in several different formats were prepared. The Acrobat version of PP901 was created by scanning the original book and converting to searchable text with optical character recognition software. The illustrations were saved as bitmaps. The entire book is present in this Acrobat document. The original book was typeset with two columns per page. In the interest of legibility on the computer display screen, the Acrobat document has been reformatted to display the columns sequentially, one column at a time, each column now filling an entire 8.5”x11” page width. For this reason, the Acrobat page breaks may differ from the original. The original page breaks are depicted by page numbers surrounded by asterisks at the top of each “original” page as in *Page 1*. Also, most of the hyphens in words continued on the next line have been eliminated. To navigate this Acrobat document, mouse-select the scroll bar on the right, bookmarks on the left, or the arrow tools in the toolbar. Use the left-double-arrow tool in the toolbar to retrace previous steps. The images can be zoomed in for greater detail using the magnifying glass tool and dragging a rectangle or the zoom pop-up on the bottom toolbar. EXPLANATORY TEXT TO ACCOMPANY THE GEOLOGIC MAP OF THE UNITED STATES By Philip B. King and Helen M. Beikman Geological Survey Professional Paper 901 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON:1974 *Page II* UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress catalog - card No. 74-600169 For Sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price $1.25 (paper cover) Stock Number 2401-02573 *Page III* CONTENTS Introduction ------------------------------------------ 1 Previous geologic maps of the United States------------- 1 Sources of information ------------------------------- 1 Maps published before 1860 -------------------------- 1 Maps between 1860 and 1880 ------------------------- 7 Maps between 1880 and 1930 ------------------------- 7 The Geologic Map of the United States of 1932 ------ 9 The Geologic Map of the United States ----------------- 10 History of the present project----------------------- 10 Sources of the Geologic Map ------------------------- 11 Uses of the Geologic Map --------------------------- 18 Methods of compilation ----------------------------- 18 Contents of the Geologic Map ------------------------ 20 Classification of the rock units -------------------- 21 Symbolization of rock units ------------------------ 25 Representation of faults ---------------------------- 28 Representation of contacts -------------------------- 31 Subcrop geology ------------------------------------- 31 Northern Interior States -------------------------- 31 Eolian deposits ---------------------------------- 35 Atlantic Coastal Plain----------------------------- 36 Radiating strikes------------------------------------ 36 References cited--------------------------------------- 38 ILLUSTRATIONS FIGURE 1. Geology of the United States as represented by Maclure (1817) --------------------------------------------------- 1 2. Geology of the United States and adjacent parts of Canada as represented by Lyell (1845) -------------------------- 4 3. Geology of the United States and adjacent parts of Canada as represented by Marcou (1855) ------------------------- 5 4. Geology of the United States and adjacent parts of Canada as represented by Edward Hitchcock (1854) ---------------- 6 5. Index map showing areas represented geologically on McGee map of 1885, areas added or revised on the McGee map of 1894, and additional coverage based on less exact information on the C. H. Hitchcock map of 1887 ------------ 8 6. Index map of Texas, showing areas covered by different sources used on the Geologic Map ------------------------- 17 7. Index map of the United States, showing areas covered by the different sources used for the subsea contours on the Geologic Map --------------------------------------------- 19 8. Geologic maps of the Sandia Mountains, New Mexico, to illustrate the process of generalizing data for the Geologic Map of the United States ------------------------ 22 9. Map of the Great Basin in Nevada and Utah, showing regional extent of major low-angle thrust faults that are represented on the Geologic Map of the United States as exposed fragments in the mountain areas ------------------ 29 1O. Circular faults shown on the Geologic Map of the United States ----------------------------------------------------30 11. Maps of eastern South Dakota, to illustrate problems of representing bedrock geology in areas with extensive cover of surficial deposits ------------------------------ 32 12. Generalized geologic map of eastern Middle Western States, to show relations of subcrop geology to preglacial river systems -------------------------------------------- 33 13. Geologic map of northern Minnesota, showing the extent of thin Upper Cretaceous deposits (Coleraine Formation) that are not represented on the Geologic Map of the United States --------------------------------------------------- 34 14. Map of western Nebraska, showing bedrock geology as represented on the Geologic Map of the United States, superposed on which are the areas of Quaternary sand dunes and drifted sand (Sand Hills Formation) as represented on the Geologic Map of the United States of 1932 and by Thorp and Smith (1952) ----------------------------------------- 35 15. Geologic map of the Atlantic Coastal Plain in Maryland, Delaware, and New Jersey, showing the relation of the bedrock units that appear on the Geologic Map of the United States to surficial deposits of Quaternary and late Tertiary age --- 37 16. Map of the southern Midcontinent region in Oklahoma, Arkansas, and Texas, showing "radiating strikes" in Paleozoic and Cretaceous rocks ------------------------------------- 38 TABLE 1. Comparison between "American" and "International" systems of coloring stratified rocks on maps --------------------- 27 *Page 1* EXPLANATORY TEXT TO ACCOMPANY THE GEOLOGIC MAP OF THE UNITED STATES By Philip B. King and Helen M. Beikman INTRODUCTION The U.S. Geological Survey has published a new Geologic Map of the United States (exclusive of Alaska and Hawaii) on a scale of 1:2,500,000, which was compiled between 1967 and 1971 by Philip B. King and Helen M. Beikman, with geologic cartography by Gertrude J. Edmonston. The map replaces the now outdated Geologic Map of the United States on the same scale, which was compiled by George W. Stose and Olof A. Ljungstedt and was issued by the U.S. Geological Survey in l932. This report is intended to supplement the new map and to provide background information to assist its user in interpreting it. It describes the historical antecedents of the map and the sources from which the map was compiled and discusses various general topics related to it. Succeeding reports will amplify the necessarily brief descriptions of the map units which appear in its legend and will deal at length with specific geological problems in the United States, insofar as they relate to representation of the features in map form. PREVIOUS GEOLOGIC MAPS OF THE UNITED STATES SOURCES OF INFORMATION Source data for previous geologic maps of the United States are plentiful, so we have chosen here to present a narrative account, describing the circumstances under which the maps were prepared and commenting on their more interesting features, rather than list details which the reader can find in the published sources. Maps that appeared before the mid-188O's have been listed and annotated by Marcou and Marcou (1884, p. 23-32) and have been described at length by C. H. Hitchcock (1887); Jillson (1950) has extended the listing to 1946. In our account we have ignored many maps that appear in these published lists as being merely reprints in the same or slightly different form by a single author, or copies of such maps in textbooks and other media. Much information on the circumstances of geologic maps published by the U.S. Geological Survey can be found in the Annual Reports of the Survey. Interesting contemporary reviews of some of the maps are cited in "Geologic literature on North America, 1785-1918" (Nickles, 1923). For our narrative, we have obtained background information from Merrill's "Contributions to the history of American Geology" down to 1880 (1906), and from biographies of later geologists, such as the Memorials of the Geological Society of America, Darrah's "Powell of the Colorado" (1951), Stegner's "Beyond the Hundredth Meridian" (1954), and Willis's autobiographical "A Yanqui in Patagonia" (1947, especially p. 30-35). Copies of most of the maps referred to here are in the files of the Library of the U.S. Geological Survey, and we are indebted to Mark Pangborn, curator of these maps, for his generous assistance. MAPS PUBLISHED BEFORE 1860 Efforts to portray on a map the geology of what is now the United States extend back more than two centuries. The first recorded attempt is a "Mineralogic map, showing the nature of the terrains of Canada and Louisiana" ("Carte minéralogique où l'on voit la nature des terrains du Canada et de la Louisiane"), by
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